![Picture](/uploads/1/0/7/0/10709207/editor/aphids.jpg?1585210735)
Pest Management
Cowpea Aphid
Aphis craccivora
DESCRIPTION OF THE PEST
Cowpea aphid is readily distinguishable from other aphids inhabiting alfalfa because it is the only black aphid found infesting the crop. It is a relatively small aphid and the adult is usually shiny black while the nymph is slate gray. The appendages are usually whitish with blackish tips.
Cowpea aphid numbers are highest from April to September; numbers peak from October to January in the desert.
This aphid has an extensive host range, including beans, cotton, and weeds.
Damage:
Cowpea aphid injects a powerful toxin into the plant while feeding and, when their numbers are high, this can stunt or even kill plants. While feeding, this aphid produces a considerable amount of honeydew upon which sooty mold can grow. The black sooty mold reduces photosynthesis and may make leaves unpalatable to livestock. The honeydew also makes the alfalfa sticky, which causes problems with harvest.
Management
There are no known varieties of alfalfa that are resistant to cowpea aphid and economic thresholds have not been developed specifically for this pest. Treatments may be necessary if large numbers of cowpea aphids are present. Border harvesting or strip cutting can be important for preserving natural enemies.
Biological Control
Two common aphid parasites, Lysiphlebus sp. and Diaeretiella sp., have been identified from the desert production areas. Although parasitism as high as 95% has been documented, aphid numbers can become so high that enough non-parasitized individuals remain to cause significant injury.
This aphid is also susceptible to the usual complement of aphid predators including lady beetles (convergent lady beetle, multicolored Asian lady beetle, twice stabbed lady beetle), lacewings, big eyed bugs, damsel bugs, and syrphid flies. Early in the season (February and early-March) many of these predators are generally not active, but in the low desert the seven spotted lady beetle, Coccinella septempunctata, is abundant and feeding on the aphid.
Chemical Control:
Lambda cyhalothrin, Deltamethrin
Cultural Control
Use border-strip cutting during harvest to help maintain populations of parasites and predators within the field.
Organically Acceptable Methods
Use biological and cultural controls on organically certified crops. Organically certified insecticides such as Azadirachtin , Neem oil and Pyrethrin are also registered for use on alfalfa to control aphids.
Monitoring and Treatment Decisions
Cowpea aphid infestations are typically patchy in a field, especially early infestations. Stems on alfalfa plants in infested areas are often completely covered with aphids, whereas plants in other areas of the field may appear aphid-free. Because of the spotty distribution of cowpea aphid infestations, spot treatments may be feasible, especially if the infestation is on the field border.
Potato Leaf Hopper
The potato leafhopper is the most important insect pest on alfalfa.
Adult potato leafhoppers are 1/8 inch long, wedge shaped, are fluorescent green in color and have wings. Nymphs have the same general appearance as adults except they: 1) can be much smaller, 2) range in color from yellowish-green to fluorescent green and 3) do not have wings.
Life cycle
Each generation takes approximately 4-5 weeks to mature and we may experience 3-4 generations/year. Potato leafhoppers can survive and cause economic damage through late summer or early fall.
Damage
Both adult and nymphs damage alfalfa by sucking plant sap and injecting a toxin back into the plant. This toxin inhibits water and nutrient transport. Damage symptoms appear as stunting as well as yellowing of the leaves in a in a v-shaped pattern starting at the tip of a leaf. Eventually, these leaves may turn completely yellow or reddish in color. As a result of this injury, there are several ways leafhopper cause economic damage. They are:
Yield loss
Quality loss, because the plant produces sugars instead of protein
Reduction in overall plant vigor, causing slower recovery of regrowth after harvest.
Chemical Control:
Lambda cyhalothrin, Deltamethrin
Cowpea Aphid
Aphis craccivora
DESCRIPTION OF THE PEST
Cowpea aphid is readily distinguishable from other aphids inhabiting alfalfa because it is the only black aphid found infesting the crop. It is a relatively small aphid and the adult is usually shiny black while the nymph is slate gray. The appendages are usually whitish with blackish tips.
Cowpea aphid numbers are highest from April to September; numbers peak from October to January in the desert.
This aphid has an extensive host range, including beans, cotton, and weeds.
Damage:
Cowpea aphid injects a powerful toxin into the plant while feeding and, when their numbers are high, this can stunt or even kill plants. While feeding, this aphid produces a considerable amount of honeydew upon which sooty mold can grow. The black sooty mold reduces photosynthesis and may make leaves unpalatable to livestock. The honeydew also makes the alfalfa sticky, which causes problems with harvest.
Management
There are no known varieties of alfalfa that are resistant to cowpea aphid and economic thresholds have not been developed specifically for this pest. Treatments may be necessary if large numbers of cowpea aphids are present. Border harvesting or strip cutting can be important for preserving natural enemies.
Biological Control
Two common aphid parasites, Lysiphlebus sp. and Diaeretiella sp., have been identified from the desert production areas. Although parasitism as high as 95% has been documented, aphid numbers can become so high that enough non-parasitized individuals remain to cause significant injury.
This aphid is also susceptible to the usual complement of aphid predators including lady beetles (convergent lady beetle, multicolored Asian lady beetle, twice stabbed lady beetle), lacewings, big eyed bugs, damsel bugs, and syrphid flies. Early in the season (February and early-March) many of these predators are generally not active, but in the low desert the seven spotted lady beetle, Coccinella septempunctata, is abundant and feeding on the aphid.
Chemical Control:
Lambda cyhalothrin, Deltamethrin
Cultural Control
Use border-strip cutting during harvest to help maintain populations of parasites and predators within the field.
Organically Acceptable Methods
Use biological and cultural controls on organically certified crops. Organically certified insecticides such as Azadirachtin , Neem oil and Pyrethrin are also registered for use on alfalfa to control aphids.
Monitoring and Treatment Decisions
Cowpea aphid infestations are typically patchy in a field, especially early infestations. Stems on alfalfa plants in infested areas are often completely covered with aphids, whereas plants in other areas of the field may appear aphid-free. Because of the spotty distribution of cowpea aphid infestations, spot treatments may be feasible, especially if the infestation is on the field border.
Potato Leaf Hopper
The potato leafhopper is the most important insect pest on alfalfa.
Adult potato leafhoppers are 1/8 inch long, wedge shaped, are fluorescent green in color and have wings. Nymphs have the same general appearance as adults except they: 1) can be much smaller, 2) range in color from yellowish-green to fluorescent green and 3) do not have wings.
Life cycle
Each generation takes approximately 4-5 weeks to mature and we may experience 3-4 generations/year. Potato leafhoppers can survive and cause economic damage through late summer or early fall.
Damage
Both adult and nymphs damage alfalfa by sucking plant sap and injecting a toxin back into the plant. This toxin inhibits water and nutrient transport. Damage symptoms appear as stunting as well as yellowing of the leaves in a in a v-shaped pattern starting at the tip of a leaf. Eventually, these leaves may turn completely yellow or reddish in color. As a result of this injury, there are several ways leafhopper cause economic damage. They are:
Yield loss
Quality loss, because the plant produces sugars instead of protein
Reduction in overall plant vigor, causing slower recovery of regrowth after harvest.
Chemical Control:
Lambda cyhalothrin, Deltamethrin
![Picture](/uploads/1/0/7/0/10709207/editor/beet-army-worm.jpg?1585211677)
Beet Army worm
Spodoptera exigua
Pupal stage is susceptible to cold temperatures. Over-wintering is usually only accomplished in the warm climates in the upper 6 cm of soil. If temperatures allow, can continue to generate populations year round.
Sampling
Traps baited with synthetic sex pheromone can be used to monitor adult populations. Traps should be checked 1-2 times per week and lure changed as recommended by the supplier. Inspect undersides of leaves and terminals for cottony egg masses. Randomly inspect plants for skeletonized leaves and other feeding damage. Sweep nets can also be used to detect larval infestations. Infestation along edges of fields may be more severe than more central locations.
MANAGEMENT
Populations of armyworms are frequently controlled by natural enemies and are more or less cyclic, occurring in large numbers only every few years. Early harvest, border cutting, and biological control are important components of a management program that will prevent damage from armyworms.
Biological Control
Natural enemies can provide good control of armyworms in many fields.
Predators include bigeyed bugs, spiders, minute pirate bugs, damsel bugs, assassin bugs, and lacewings.
The parasitic wasp, Hyposoter exiguae, is the most important of at least 10 parasites attacking this pest.
Viral diseases of armyworms are also important natural control agents under certain conditions of temperature and humidity. Diseased caterpillars first appear yellowish and limp. After death they hang from plants as shapeless forms oozing the disintegrated body contents.
Cultural Control
Biological and cultural controls, as well as sprays of Bacillus thuringiensis, Spinosad and Neem formulations are acceptable for use on an organically certified crop..
Indoxacarb, Emamectine benzoate, Deltamethrin, Lambda cyhalothrin, Bt
Spodoptera exigua
- Beet Armyworm has wide range of host plants that include: alfalfa, asparagus, bean, beet, broccoli, cabbage, cauliflower, celery, chickpea, corn, cotton, cowpea, eggplant, lettuce, onion, pea, peanut, pepper, potato, radish, safflower, sorghum, soybean, spinach, sugarbeet, sweet potato, tobacco, tomato, and turnip.
- Weeds that serve as hosts include: lambs quarter, mullein, nettle leaf goosefoot, parthenium, pigweed, purslane, Russian thistle and tidestromia.
- In general, control measures are more effective on smaller larva than more advanced stages of development.
- Adults are strong fliers. Beet armyworm migrate from over-wintering sites as summer progresses.
- Mass migratory infestations can occur when preferred hosts are no longer available due to lack of moisture and other environmental conditions.
- Armyworms skeletonize foliage, leaving veins largely intact. First- and second- instar larvae tend to feed in clusters around the egg mass from which they hatch. This frequently causes a tattered appearance to the terminals. This whitish appearance caused by the feeding is known as "whitecaps" and can be seen across a field. As the larvae mature and move to more stems, the areas of "whitecaps" tend to coalesce and the entire field takes on a tattered look.
- Broad-spectrum insecticide use can reduce natural controls and increase Beet Armyworm survival rates.
- Sex pheromone is used for mating recognition.
- Eggs: (2-3 Days). Laid in groups of 50-150. Usually found on the undersides of leaves and terminals. Taper to a peak when viewed from the side. White to green in color. White scales are deposited on top of cluster by the female moth that give the egg mass a cottony appearance.
- Larva : (11-25 Days) 5 instars. Variable coloration – light to dark green or pink with a white or dark stripe running the length of both sides of the body. Identifying characteristics include a smooth body with no hairs and large dark spots on both sides of the body just behind the head. Young larva feed in groups around the area of the egg hatch and may produce webbing as they feed. Mature larva feed singly.
- Pupa: (6-7 Days). 15-20 mm. Light brown. Pupal case consists of soil, sand or other ground debris loosely held together by oral secretions.Adult: (9-10 Days). 25-30 mm. Mottled brown or gray. Can deposit 300-600 eggs/female. Mating can occur shortly after emergence from pupa. Eggs begin to be deposited 2-3 days after fertilization and can continue for 3-7 days. Mainly nocturnal.
Pupal stage is susceptible to cold temperatures. Over-wintering is usually only accomplished in the warm climates in the upper 6 cm of soil. If temperatures allow, can continue to generate populations year round.
Sampling
Traps baited with synthetic sex pheromone can be used to monitor adult populations. Traps should be checked 1-2 times per week and lure changed as recommended by the supplier. Inspect undersides of leaves and terminals for cottony egg masses. Randomly inspect plants for skeletonized leaves and other feeding damage. Sweep nets can also be used to detect larval infestations. Infestation along edges of fields may be more severe than more central locations.
MANAGEMENT
Populations of armyworms are frequently controlled by natural enemies and are more or less cyclic, occurring in large numbers only every few years. Early harvest, border cutting, and biological control are important components of a management program that will prevent damage from armyworms.
Biological Control
Natural enemies can provide good control of armyworms in many fields.
Predators include bigeyed bugs, spiders, minute pirate bugs, damsel bugs, assassin bugs, and lacewings.
The parasitic wasp, Hyposoter exiguae, is the most important of at least 10 parasites attacking this pest.
Viral diseases of armyworms are also important natural control agents under certain conditions of temperature and humidity. Diseased caterpillars first appear yellowish and limp. After death they hang from plants as shapeless forms oozing the disintegrated body contents.
Cultural Control
- Border-strip harvesting is a useful method for preserving natural enemies because it helps retain parasite larvae in the field. Early cutting will give satisfactory control if the infestation appears late in the cutting cycle.
- Plant Sunflower or Castor on borders as oviposition trap crops, adult moths prefer to lay eggs on these plants, clip off the egg masses and destroy to reduce the population.
- Maintain good fertility and mineral balance in plants. Identify macro- and micronutrient deficiencies by performing plant tissue and soil analysis. Adjust for deficiencies with foliar and soil applied applications of appropriate fertilizers.
- Destroy vegetative materials and crop residue immediately after harvest.
Biological and cultural controls, as well as sprays of Bacillus thuringiensis, Spinosad and Neem formulations are acceptable for use on an organically certified crop..
- Commonly Used Products
- Cold Processed 100% Neem Oil
- Cold Processed 100% Karanja Oil
- Neem Pro EC
- Garlic Oil
- Bt:
- Azadirachtin
Indoxacarb, Emamectine benzoate, Deltamethrin, Lambda cyhalothrin, Bt
![Picture](/uploads/1/0/7/0/10709207/editor/weevil.jpg?1585212076)
Alfalfa weevil
The alfalfa weevil is a small, brown, snout-nosed beetle approximately 3/16 inch in length with a wide dark stripe down its back. The larva is green with a black head and a white stripe down its back. Both the adult and larvae feed on alfalfa foliage. Foliar feeding injury by the adult is not significant. Foliar injury by 1st and 2nd instars is primarily confined to the growing tips. Late 3rd and 4th instars may extensively defoliate alfalfa when abundant.
Control:
Spray repellents like Azadirachtin (Neem), Cedar oil spray formulations or other Bio-pesticides.
Chemical control:
Indoxacarb, Emamectine benzoate, Deltamethrin, Lambda cyhalothrin
The alfalfa weevil is a small, brown, snout-nosed beetle approximately 3/16 inch in length with a wide dark stripe down its back. The larva is green with a black head and a white stripe down its back. Both the adult and larvae feed on alfalfa foliage. Foliar feeding injury by the adult is not significant. Foliar injury by 1st and 2nd instars is primarily confined to the growing tips. Late 3rd and 4th instars may extensively defoliate alfalfa when abundant.
Control:
Spray repellents like Azadirachtin (Neem), Cedar oil spray formulations or other Bio-pesticides.
Chemical control:
Indoxacarb, Emamectine benzoate, Deltamethrin, Lambda cyhalothrin
![Picture](/uploads/1/0/7/0/10709207/editor/locust.jpg?1585212726)
Locust
Locusts are the short-horned grasshoppers with highly migratory habit, marked polymorphism and voracious feeding behavior. They are capable of forming swarms (adult’s congregation) and hopper bands (nymphal congregation). They cause great devastation to natural and cultivated vegetation. They are indeed the sleeping giants that can flare up any time to inflict heavy damage to the crops leading to national emergency of food and fodder.
Life cycle:
Locust life cycle has three distinct stages (i) Egg, (ii) Hopper and (iii) Adult.
Egg: Eggs are laid in pods in moist sandy soil at a depth of about 10 cms at an interval of 7 – 10 days. Gregarious female usually lay 2-3 egg pods having 60-80 eggs in average. Solitarious female mostly lay 3-4 times having 150-200 eggs in average. The rate of development of eggs depends on soil moisture and temperature. No development takes place below 15°C. The incubation period is 10-12 days when the optimum temperature is between 32-35°C.
Hopper: After incubation is complete the eggs hatch and nymph (young ones) emerge. There are 5 instars in gregarious and 5-6 instars in solitarious population. In each instars there is a growth and change in characteristic coloration
The rate of development in hopper depends on temperature. It takes 22 days when the mean air temperature is hot say about 37°C and may be delayed up to 70 days when the mean temperature is cold say about 22°C.
Adult: The Fifth Instar adult moults into adult stage. This change is called 'fledging' and the young adult is called 'fledgling' or 'immature adult' means they are sexually immature. The period of sexual maturity varies. In suitable condition the adult may mature in 3 weeks and under cool and /or dry condition it may take 8 months time. During this stage the adults fly for search of favorable breeding condition and may cover thousands of kilometers.
Young immature adults are pink in color but old ones become dark red or brown in cold condition. On maturation the adults become bright yellow. Males mature before females. Oviposition commences within two days of copulation
Newly sown Lucerne up to the 5th trifoliate leaf stage may be at risk of significant damage. Crops at the cotyledon stage were badly damaged. Lucerne after the 5th trifoliate leaf stage with a developed crown has a better chance of recovery from damage. As Lucerne is often green for longer and over summer when there is little other green vegetation it can become a target. Damage is restricted to stripping of leaves, similar to heavy grazing but the crown is rarely damaged.
Control:
Green Muscle ® contains spores of the naturally occurring fungus Metarhizium anisopliae var. acridum, which germinate on the skin of locusts and penetrate through their exoskeletons. The fungus then destroys the locust's tissues from the inside.
Chemical control:
Fenitrothion, Fipronil, Bendiocarb
Locusts are the short-horned grasshoppers with highly migratory habit, marked polymorphism and voracious feeding behavior. They are capable of forming swarms (adult’s congregation) and hopper bands (nymphal congregation). They cause great devastation to natural and cultivated vegetation. They are indeed the sleeping giants that can flare up any time to inflict heavy damage to the crops leading to national emergency of food and fodder.
Life cycle:
Locust life cycle has three distinct stages (i) Egg, (ii) Hopper and (iii) Adult.
Egg: Eggs are laid in pods in moist sandy soil at a depth of about 10 cms at an interval of 7 – 10 days. Gregarious female usually lay 2-3 egg pods having 60-80 eggs in average. Solitarious female mostly lay 3-4 times having 150-200 eggs in average. The rate of development of eggs depends on soil moisture and temperature. No development takes place below 15°C. The incubation period is 10-12 days when the optimum temperature is between 32-35°C.
Hopper: After incubation is complete the eggs hatch and nymph (young ones) emerge. There are 5 instars in gregarious and 5-6 instars in solitarious population. In each instars there is a growth and change in characteristic coloration
The rate of development in hopper depends on temperature. It takes 22 days when the mean air temperature is hot say about 37°C and may be delayed up to 70 days when the mean temperature is cold say about 22°C.
Adult: The Fifth Instar adult moults into adult stage. This change is called 'fledging' and the young adult is called 'fledgling' or 'immature adult' means they are sexually immature. The period of sexual maturity varies. In suitable condition the adult may mature in 3 weeks and under cool and /or dry condition it may take 8 months time. During this stage the adults fly for search of favorable breeding condition and may cover thousands of kilometers.
Young immature adults are pink in color but old ones become dark red or brown in cold condition. On maturation the adults become bright yellow. Males mature before females. Oviposition commences within two days of copulation
Newly sown Lucerne up to the 5th trifoliate leaf stage may be at risk of significant damage. Crops at the cotyledon stage were badly damaged. Lucerne after the 5th trifoliate leaf stage with a developed crown has a better chance of recovery from damage. As Lucerne is often green for longer and over summer when there is little other green vegetation it can become a target. Damage is restricted to stripping of leaves, similar to heavy grazing but the crown is rarely damaged.
Control:
Green Muscle ® contains spores of the naturally occurring fungus Metarhizium anisopliae var. acridum, which germinate on the skin of locusts and penetrate through their exoskeletons. The fungus then destroys the locust's tissues from the inside.
Chemical control:
Fenitrothion, Fipronil, Bendiocarb
![Picture](/uploads/1/0/7/0/10709207/published/rodents.jpg?250)
Rodent Management
Rodents damage alfalfa by feeding on alfalfa roots and stems. They are active all year and are normally found in areas with dense ground cover. They dig short, shallow burrows and make underground nests of grass, stems, and leaves.
Preventing rodent damage usually requires a management program that keeps down the population in the area. If appropriate, the first step is to remove or reduce the vegetative cover. Preventing rodent damage usually requires a management program that keeps down the population in the area. Removing cover also makes detecting rodents easier. A program to control the rodents population may be necessary. Because the damage rodents do to alfalfa can be quite severe, and because of their rapid reproductive rate, initiating a program of habitat modification and/or population reduction before their numbers explode is important.
Habitat Modification. When practical, habitat modification is particularly effective in deterring rodents. Once they are established in the field however, habitat modification is not applicable since the alfalfa provides an excellent rodent habitat. Weeds, heavy mulch, and dense vegetative cover encourage rodents by providing food and protection from predators and other environmental stresses. Clearing grassy and weedy areas adjacent to alfalfa fields can be helpful in preventing damage because it will reduce the base area from which rodents invade. Weed-free strips can serve as buffers around areas to be protected. The wider the cleared strip, the less apt rodents will be to cross and become established in alfalfa. A minimum width of 15 feet is recommended, but even that might not be enough when rodent numbers are high.
Toxic Bait. When rodents are numerous or when damage occurs over large areas you may need to use toxic bait to achieve adequate control. When you use toxic baits, take care to ensure the safety of children, pets, and non-target animals. Do this by following product label instructions carefully. Zinc phosphide* treated grain baits (200% ) are very effective in controlling rodent populations in alfalfa. There are no established crop tolerances for zinc phosphide in alfalfa, therefore it can be applied only during the dormant season of growth. The most effective method of application is to broadcast the grain bait over the alfalfa. This enables the rodents to find the bait on the runways and near burrow entrances
Natural Control. Predators, especially barn owls and hawks eat rodents. Barn owl nest boxes are being promoted by some to assist in the rodent control efforts.
Monitoring Guidelines. To detect the presence of rodents, look for fresh trails in the grass, as well as burrows, droppings, and evidence of feeding. Routine monitoring of the alfalfa field and surrounding area is important. Pay particular attention to adjacent areas that have heavy vegetation because rodents can build up in these areas and invade the alfalfa field.
Rodents damage alfalfa by feeding on alfalfa roots and stems. They are active all year and are normally found in areas with dense ground cover. They dig short, shallow burrows and make underground nests of grass, stems, and leaves.
Preventing rodent damage usually requires a management program that keeps down the population in the area. If appropriate, the first step is to remove or reduce the vegetative cover. Preventing rodent damage usually requires a management program that keeps down the population in the area. Removing cover also makes detecting rodents easier. A program to control the rodents population may be necessary. Because the damage rodents do to alfalfa can be quite severe, and because of their rapid reproductive rate, initiating a program of habitat modification and/or population reduction before their numbers explode is important.
Habitat Modification. When practical, habitat modification is particularly effective in deterring rodents. Once they are established in the field however, habitat modification is not applicable since the alfalfa provides an excellent rodent habitat. Weeds, heavy mulch, and dense vegetative cover encourage rodents by providing food and protection from predators and other environmental stresses. Clearing grassy and weedy areas adjacent to alfalfa fields can be helpful in preventing damage because it will reduce the base area from which rodents invade. Weed-free strips can serve as buffers around areas to be protected. The wider the cleared strip, the less apt rodents will be to cross and become established in alfalfa. A minimum width of 15 feet is recommended, but even that might not be enough when rodent numbers are high.
Toxic Bait. When rodents are numerous or when damage occurs over large areas you may need to use toxic bait to achieve adequate control. When you use toxic baits, take care to ensure the safety of children, pets, and non-target animals. Do this by following product label instructions carefully. Zinc phosphide* treated grain baits (200% ) are very effective in controlling rodent populations in alfalfa. There are no established crop tolerances for zinc phosphide in alfalfa, therefore it can be applied only during the dormant season of growth. The most effective method of application is to broadcast the grain bait over the alfalfa. This enables the rodents to find the bait on the runways and near burrow entrances
Natural Control. Predators, especially barn owls and hawks eat rodents. Barn owl nest boxes are being promoted by some to assist in the rodent control efforts.
Monitoring Guidelines. To detect the presence of rodents, look for fresh trails in the grass, as well as burrows, droppings, and evidence of feeding. Routine monitoring of the alfalfa field and surrounding area is important. Pay particular attention to adjacent areas that have heavy vegetation because rodents can build up in these areas and invade the alfalfa field.